The DOD's Servicemembers Civil Relief Act site, at https://www.dmdc.osd.mil/scra/owa/home, can supply you with an affidavit stating if the individual is on active duty or not. You need to know the requested information, however.
This affidavit is generally sufficent for judges in Illinois. You would have to check with your Judge to determine if it is acceptable there.
Disclaimer: This answer is provided as a public service and as a general response to a general question, it is not meant, and should not be relied upon as specific legal advice, nor does it create an attorney-client relationship.